Two Americans who contracted Ebola in Africa received an experimental serum

As the health of two Ebola-stricken American missionaries deteriorated late last month, an international relief organization backing them hunted for a medical miracle. The clock was ticking, and a sobering fact remained: Most people battling the disease do not survive.

Leaders at Samaritan’s Purse, a North Carolina-based Christian humanitarian group, asked officials at the Centers for Disease Control and Prevention whether any treatment existed — tested or untested — that might help save the lives of Kent Brantly and Nancy Writebol, both of whom had contracted Ebola while helping patients in Liberia.

The CDC put the group in touch with National Institutes of Health workers in West Africa, where an employee knew about promising research the U.S. government had funded on a serum that had been tested only in monkeys.